The National Fire Protection Association (NFPA) has published the National Electrical Code® (NEC®) since 1911. From inception, lighting/surge arrestors have been addressed, now detailed in Article 280 of the Code. With the proliferation of sensitive electronic equipment such as computers, answering machines, microwaves, etc., higher-grade protection products were needed. Transient Voltage Surge Suppressors (TVSS) or Surge Protection Devices (SPDs) are the newest products designed to protect sensitive electronics.Article 285 was introduced into the 2002 NEC to address proper installation of this new generation of surge suppressor. This compliments UL 1449, which is the product standard.
|At a Glance: |
Article 285 is intended to guide the electrician toward proper installation of hardwired TVSS/SPDs. Also, provisions are made for electrical inspectors to ensure proper safety and fault current coordination where TVSS/SPDs are installed. Surge protection plug-strips are not hard-wired and do not fall under the jurisdiction of the NEC.
Key elements of the Article 285 include:
- non-permitted usage (such as ungrounded distribution systems),
- requirements of using Listed devices,
- general installation guidelines, and
- new fault current requirements.
Article 285.6 requires all TVSS/SPDs to be marked with a short circuit current rating (SCCR). This rating must be equal or greater than the available fault current present at the point where the TVSS/SPD is installed on the system. For example, if a protector is to be installed at a service entrance location where the available fault current is 100kA symmetrical amperes, then the SPD or TVSS needs to be rated and carry a SCCR of 100kA or greater. This rating is derived from actual testing.
NFPA 780, Standard for the Installation of Lightning Protection Systems, 2011 Edition
This standard is intended to provide requirements, within the limits of the current state of knowledge, for the installation of those lightning protection systems covered by the standard.
Chapter 4: Protection for Ordinary Structures
Section 4.18 – Surge Protection.
Article 285 is part of NEC 2011 (a.k.a. NFPA 70) and it can be purchased online (www.nfpa.org).